add integration tests

[Travis Vachon]

Chatted with @olizilla and @yusefnapora this morning and we are inclined to do browser testing with some third party service that makes it easy and low maintenance. Need to investigate the state of the art for this kind of testing.

[Oli Evans]

There's "the test framework" and "the cloud test service", and some frameworks can be run by multiple services

test framework	cloud service	feels like
cypress	cypress cloud, browserstack, lambdatest	mocha + chai
@playwright/test	lambdaTest	ava + expect (but you can drive playwight from any test framework)

[Oli Evans]

Added integration tests using @playwright/test to drive the browser orchestration in #242 as the first part of this. I think the scope of this issue should be "have integrations tests we are happy with". We can adopt a testing service if we find friction or features that we need.